In the area of reproductive physiology we wish to determine: 1) the neural and endocrine factors which are implicated in the transition of the anestrous ewe to first heat; 2) whether alterations in gonadotropin and prolactin levels occur in male odor-stimulated responses in female mice, and whether the changes are the same in estrus synchronization, pregnancy block, and advancement of puberty; and 3) whether extracts can be prepared from testes which are capable of selectively depressing FSH levels, and to identify the responsible factors in such extracts. Objectives of other studies are: 1) to continue to explore the mode of action of MSH in promoting darkening of hair in agouti mice, trying to determine whether effects on color, tyrosinase activity, and pigment granule ultrastructure are interdependent; 2) to examine further the contribution of serotonin in the control of MSH release; 3) to evaluate the possibility of an intercellular site of action of polypeptide hormones and catecholamines; 4) to analyze the changes in prolactin and GH during stimulation of ruminant growth by diethylstilbestrol; and 5) to purify further pharmacologically-active compound(s) of the urophysis and to attempt to develop a system for maintenance of the urophysis in organ culture.